The present invention relates generally to the handling of sheet material and more particularly to an apparatus adapted for attachment to a fork lift truck for the transport of a stack of vertically supported fragile sheet material, such as glass, for example.
In the glass industry it is customary for convenience and ease of handling to store sheets of glass, such as automotive and architectural glass on edge in a generally upright position for processing, shipping, and storage. The sheets are individually stacked on transport pallets, racks, or in shipping containers at the end of a processing line either manually or automatically by sheet handling devices which are prevalent in present manufacturing facilities. The number of sheets in individual stacks vary depending on need and current use.
It is often necessary to transfer a stack of sheets from one support or container to another. This need arises, for example, in factory warehouses where sheets are transferred from a temporary support utilized during processing to permanent type racks utilized to store glass for future use. Conversely, the need to transfer a stack of sheets from a permanent storage rack to a pallet or shipping container, for example, also arises. A similar need manifests itself in the supply industry wherein warehouses are established for storing, for example, automotive glass for the glass replacement market and architectural glass for the building industry. The glass sheets are typically shipped to the supply warehouses in shipping containers accommodating a plurality of vertically supported sheets, The sheets are then transferred from the shipping containers to permanent storage racks where they are stored until needed.
Typically, to transfer a stack of sheets from one location to another, for example, from a shipping container or pallet to a storage rack, it has been customary to manually remove one sheet at a time from the shipping container and transfer it to the storage rack. Such a procedure is very time consuming and laborious adding to the cost of the operation. Transferring each sheet individually also increases the potential for accidental damage to the glass sheets or injury to the handler.
An early attempt at transporting a plurality of vertically disposed plates is disclosed in U.S. Pat. No. 1,753,578. The invention relates to a conveyor hook suspended from an overhead block and is particularly adapted for transporting a plurality of identical units, such as steel plates or the like, placed in edgewise relation from a storage rack.
More recently, an improved sheet handling device for moving a vertically supported batch of sheets has been developed, as disclosed in U.S. Pat. No. 4,522,544. The device is suspended from a lifting hook of a crane and is designed to separate a batch of sheets from a stack or add a batch to a stack. The device makes it more practical to store and transport larger stacks of sheets.
A gripper apparatus preferably mounted on the end of a robot arm for stacking a batch of glass sheets is disclosed in U.S. Pat. No. 4,673,325. The apparatus comprises a gripper head having a sheet support for movement to grip the batch of sheets, a roller stop at the bottom of the support and at least one clamp movable at the top of the support to grip the batch against the sheet support.
Although the above sheet handling apparatus are important advancements in the expeditious transferring of a stack of sheets from one location to another, they do present certain limitations in that the range of transfer is confined to the reach of the overhead conveyor in the first two mentioned systems and the robot in the last mentioned system.
U.S. Pat. No. 4,394,106 discloses a glass pack lifting frame which is adapted to attach to the lift mast of an industrial lift truck. The lifting frame includes gripping devices at the sides for engaging the sides of the glass pack and feet at the bottom for supporting the bottom of the pack. The invention provides a lift mechanism with greater range for accurate placement and orientation of a pack of glass sheets. While the mechanism is well suited for handling large sheets of glass, the size and relatively complex structure of the mechanism would present certain limitations for handling sheets of substantially smaller proportions.